I thought she was still defending too, but when looking at the replay I saw Weili's left arm go limp when Rose's first hammerfist lands. To me, it was a fair stoppage at that point. You know Dana was already itching for a rematch during the after fight presser.
Her arm doesn’t go limp, Rose is holding her arm down so she can’t block the punches. She only gets hit twice and the ref stops it. Definitely an early stoppage especially in a title fight.